Sight ID

• Phylum Arthropoda

• Subphylum-Chelicerata

• Class Arachnida

• Loxoscles reclusa –Brown Recluse

• Distribution in TN: Statewide

• Distribution in US: Southeast

1

ID Marks• Fiddle on cephalothorax w/ neck of

fiddle toward abdomen• Abdomen has no spots or stripes• Legs are a single color

Target Objectives for

Arthropods

• Describe the characteristics of arthropods.

• Explain the main adaptations contributing to arthropod success.

• List the four main groups of arthropods and describe the features of each.

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3

Phylum Arthropoda

Section 21.8

Phylum Arthropoda: Trilobites, chelicerates, myriapods, crustaceans, and insects

Arthropods Have Jointed Appendages

Over 1,000,000 species of arthropods exist!

Figure 21.2

Section 21.8 Figure 21.18

Key features

Arthropods Have Jointed Appendages

6

Phylum Arthropoda

• “jointed foot”

• Largest phylum

• 900,000 species– 75% of all known

species

• Insects, spiders, crustaceans, millipedes, scorpions, ticks, etc.

7

Phylum Arthropoda (cont’d)

• Most successful phylum– Ecologically diverse

– Present in all regions of the earth

• Adapted to air, land, freshwater, marine, other organisms

Arthropod Origins

• The arthropod body plan consists of a segmented body, hard exoskeleton, and jointed appendages

• This body plan dates to the Cambrian explosion (535–525 million years ago)

• Early arthropods show little variation from segment to segment

© 2011 Pearson Education, Inc.

Figure 33.28

• Arthropod evolution is characterized by a decrease in the number of segments and an increase in appendage specialization

• These changes may have been caused by changes in Hox gene sequence or regulation

© 2011 Pearson Education, Inc.

Figure 33.29EXPERIMENT

Origin of Ubx andabd-A Hox genes?

RESULTS

Common ancestor

Otherecdysozoans

Arthropods

Onychophorans (velvet worms)

Ant antennaJ jawsL1–L15 body segments

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Reasons for success

1. Versatile exoskeleton

2. Efficient locomotion

3. Air piped directly to cells (terrestrial)

4. Highly developed sensory organs

5. Complex behavior

6. Metamorphosis

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1. Exoskeleton– External: not enveloped by living tissue

– Protection

– Secreted by underlying epidermis

• Waterproof barrier

• Chitin +/- calcium, lipoproteins

• Modifications

– Can be site for muscle attachment

– Energy stores- flying

– Sensory receptors

– Gas exchange

– bristles

14

1. Exoskeleton (cont’d)– Varies from soft and permeable to hard,

impermeable

– Between segments of body/appendages= thin + flexible

– Must be shed (ecdysis= molting) to allow growth

– Relatively heavy

• Limits size

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2. Efficient locomotion– Tagmatization, more specialized than annelids

• Regions= tagma/tagmata

• Jointed appendages

Crayfish mouthparts

Crushing food Food handling Drawing water into gills

Touch, taste, food handling

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3. Air piped directly to cells– More efficient than

most other invertebrates

• Most have efficient tracheal system of air tubes; some breathe by gills

• Limits size

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4. Highly developed sense organs• Sight, touch, smell, hearing, balance, chemical

reception

Displacement of seta initiates

a nerve impulse in a receptor

cell at its base

Eyes convert light energy into

nerve impulses

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5. Complex behavior patterns• Complex, organized activities

• May be innate (unlearned) or learned

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6. Limited intraspecific competition– Many arthropods undergo metamorphosis

• meta= between/after; morphē= form; osis= state of

– Different stages (ie. larva, adult) have different nutrition/habitats no competition

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Research questions

• What is metamorphosis and why has it contributed to arthropod success?

• What phylum is most closely related to Phylum Arthropoda?

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Arthropod Groups

1. Subphylum Trilobita - extinct trilobites

2. Subphylum Chelicerata– horseshoe crabs, spiders, ticks, mites, and

some extinct groups

3. Subphylum Myriapoda– centipedes, millipedes

4. Subphylum Crustacea– crabs, lobsters, shrimps, barnacles

5. Subphylum Hexapoda– Insects

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Subphylum Trilobita

• tri= three; lobos= lobes

• Divided into 3 longitudinal regions

• Extinct

• Oval, flattened

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Subphylum Chelicerata

• Named for claw-like feeding appendage called chelicerae

• Horseshoe crabs, spiders, ticks, mites, scorpions

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Subphylum Chelicerata (cont’d)

• Cephalothorax – Fused head and thoracic region

– 6 pairs of appendages

• Abdomen– contains digestive,

reproductive, excretory, and respiratory organs

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Subphylum Chelicerata (cont’d)

• Appendages attached to cephalothorax– Pair of chelicerae (clawlike feeding appendages)

– Pair of pedipalps (usually sensing or feeding)

– four pairs of legs (5 in horseshoe crabs)

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Subphylum Chelicerata (cont’d)

• No antennae

• Most suck liquid food from prey

mite

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Class Arachnida

• Spiders, ticks, scorpions

• Most are predaceous

Scorpion

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Class Arachnida (cont’d)

• Most are harmless/beneficial to humans

• Some spiders (ie. black widow, brown recluse spider) give painful, dangerous bites

Black

widowBrown

recluse

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Class Arachnida (cont’d)

• Scorpion sting can be painful, dangerous

Scorpion

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Class Arachnida (cont’d)

• Some ticks and mites spread disease, cause irritation

Dust mite mite

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Class Arachnida (cont’d)

• Lyme disease– Caused by tick

tick

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More on spiders……

Order Araneae

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Spiders

• cephalothorax and abdomen shows no external segmentation

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Spiders (cont’d)

• All predaceous– Mostly insects

• Chelicerae have fangs

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Spider Urban legends

Debunked!

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• MYTH: Daddy longlegs (Harvestmen) are one of the most poisonous spiders but their fangs are too short to bite humans: MYTH (!!!!!!!)

• Daddy longlegs: Order Opilionid

• Spiders: Order Araneae

• One basic body segment (no pedicel)

• Don’t produce silk

• No venom, fangs

daddy longlegs

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Spiders: Class Araneae

Spider love…..

• Spiders, like most arthropods, are dioecious

• Mating habits– Pheromones- chemicals that elicit behavioral

change

– Rituals- males pluck female’s web (pattern is species-specific)

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Spiders: Class Araneae

• Male builds small web, deposits sperm– Collects sperm in cavities of pedipalps

– Pedipalps have ejaculatory duct

– inserts pedipalps into female genital opening

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Spiders: Class Araneae

• Eggs laid in silk case– Carried, attach to web, bury

Wolf spider preparing egg sac

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A lycosid (wolf spider) preparing egg sac

M. C. Barnhart

48M. C. Barnhart

49M. C. Barnhart

50M. C. Barnhart

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Wolf spider parental care- after

the eggs hatch, the young ride on

mom for several days.

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Brown recluse

• Violin-shaped stripe

on back

• Necrotoxin

– hemolytic

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Loxosceles reclusa

• Necrosis of tissue

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Day 3

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Day 4

56

Day 5

57

Day 6

58

Day 9

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Day 10

Myriapods

• Subphylum Myriapoda includes millipedes and

centipedes

• Myriapods are terrestrial, and have jaw-like

mandibles

• Millipedes eat decaying leaves and plant matter

• Millipedes have many legs, with two pairs per

trunk segment

© 2011 Pearson Education, Inc.

• Centipedes are carnivores

• Centipedes have one pair of legs per trunk

segment

© 2011 Pearson Education, Inc.

Figure 33.34b

(b) Centipede

Figure 33.34

(a) Millipede

(b) Centipede

Target Objectives for Arthropods

• Describe the characteristics of arthropods.

• Explain the main adaptations contributing

to arthropod success.

• List the four main groups of arthropods

and describe the features of each.

64

Insecta

• Subphylum Hexapoda, insects and relatives, has

more species than all other forms of life combined

• They live in almost every terrestrial habitat and in

fresh water

• The internal anatomy of an insect includes several

complex organ systems

© 2011 Pearson Education, Inc.

Grasshopper External Anatomy

• Head

– Clypeus

– Labrum

– Mandible

– Maxilla

– Labium (lower jaw)

– Frons

– Gena (cheeks)

Grasshopper External Anatomy

• Head

– Clypeus

– Labrum

– Mandible

– Maxilla

– Labium (lower jaw)

– Frons

– Gena (cheeks)

Grasshopper External

Anatomy• Body

– Thorax -Head -Forewing -Tympanum

• Prothorax -Abdomen -Hindwing -Leg

• Mesothorax -Antenna -Spiracles

• Metathorax -Eye -Ovipositor

Grasshopper External Anatomy

• Leg

– Claws

– Coxa

– Femur

– Tibia

– Tibial Spurs

– Trochanter

– Tarsus

Abdomen Thorax Head

Compound eye

Antennae

Heart Dorsalartery Crop Cerebral

ganglion

MouthpartsNerve cordsTracheal tubes

Ovary

Malpighiantubules

Vagina

Anus

Figure 33.35

• Insects diversified several times following the

evolution of flight, adaptation to feeding on

gymnosperms, and the expansion of angiosperms

• Insect and plant diversity declined during the

Cretaceous extinction, but has been increasing in

the 65 million years since

© 2011 Pearson Education, Inc.

• Flight is one key to the great success of insects

• An animal that can fly can escape predators, find

food, and disperse to new habitats much faster

than organisms that can only crawl

© 2011 Pearson Education, Inc.

Figure 33.36

• Many insects undergo metamorphosis during their

development

• In incomplete metamorphosis, the young, called

nymphs, resemble adults but are smaller and go

through a series of molts until they reach full size

© 2011 Pearson Education, Inc.

Life Cycle

Simple Metamorphosis

• Insects with complete metamorphosis have

larval stages known by such names as maggot,

grub, or caterpillar

• The larval stage looks entirely different from the

adult stage

© 2011 Pearson Education, Inc.

Figure 33.37

(a) Larva (caterpillar)(b) Pupa

(c) Later-stage

pupa (d) Emerging

adult

(e) Adult

• Most insects have separate males and females

and reproduce sexually

• Individuals find and recognize members of their

own species by bright colors, sound, or odors

• Some insects are beneficial as pollinators, while

others are harmful as carriers of diseases, or

pests of crops

• Insects are classified into more than 30 orders

© 2011 Pearson Education, Inc.

Archaeognatha (bristletails; 350 species)

Thysanura (silverfish; 450 species)

Winged insects (many orders)

Complete metamorphosis

Coleoptera

(beetles; 410,000 species)

Diptera

(151,000 species)

Hymenoptera

(125,000 species)

Lepidoptera

(120,000 species)

Orthoptera

(13,000 species)

Hemiptera

(85,000 species)

Incomplete metamorphosis

Figure 33.38

/

/

Orders to know

The Grasshopper: the

digestive system• Grasshoppers feed on plants so their

mouthparts are modified for cutting & chewing plant materials

• The labrum & labium are mouthparts that function as upper & lower lips

• They hold the food in place so the sharp mandibles & maxillae can cut it

• The food is moistened by saliva, passes through the esophagus & into the crop for temporary storage

The digestive system…

• The food then pass into the gizzard where

it is ground & shredded & is pushed into

the midgut

• In the midgut, enzymes are released to

digest the food & nutrients are absorbed

• Undigested matter enters the hindgut &

leaves the body

82

The Grasshopper: Circulatory

system

• Nutrients are transported through the body of a

grasshopper by an open circulatory system

• Hemolymph (blood) flows through a large dorsal

vessel called the aorta

• The heart is located in the abdomen & thorax pumps

the hemolymph towards the head where it slowly

moves through a sieve like structure called a

coelom

• The hemolymph then slowly makes its way back to

the heart to be recirculated

84

How do circulatory systems compare?

The Grasshopper: nervous

system• The central nervous system consists of a brain & a

ventral nerve cord with ganglia located in each body segment

• Ganglia are small nerve centers that control each segment & boost signals from the brain

• In the head, nerves extend from the brain to the sensory organs:

– Antennae: touch & smell

– Simple eyes: measure light intensity

– Compound eyes: composed of hundreds of lenses provide a wide field of vision & detect motion

• Other nerves extend from the segment

ganglia to the muscles

• The abdominal ganglia connects to a sound

sensing organ called the tympanum

– It is an oval window found on the first

abdominal segment which is hollow & full

of air

– Sounds cause the tympanum to vibrate,

sending a signal to the nearby nerves that

are interpreted as sound

87

Crustaceans

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The Crustaceans

shrimpcrabs

lobsters

amphipods

euphausids

(krill)amphipods

Daphnia

• Phylum Arthropoda– Subphylum Crustacea

• crusta= shell

• Lobster, crayfish, shrimp, crab, water flea, barnacles

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The Crustaceans (cont’d)

• Aquatic (mostly marine)– a few terrestrial forms

• Major ecological and economical importance.

shrimp

lobsters

euphausids

(krill)amphipods

91

• Only arthropods with 2 pairs of antennae

Antennae

Antennules

Crayfish External Anatomy

92

Crayfish External Anatomy

93

94

• Great specialization of appendages– Mouthparts chewing, grinding, handling

95

– appendages strengthened for walking or protection (chelipeds, pincer-like claws)

cheliped

walking legs

Digestive• The cardiac

stomach has 3 teeth that grind food called the gastric mill

96

Gastric Mill

Digestive• Crayfish also

have a liverthat produces digestive enzymes and enters the midgut through ducts (nearly identical to ours)

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Digestive

• Crayfish eat snails, tadpoles, insects, larvae, decaying matter

• Mostly Nocturnal

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Digestive

• Digestive Pathway:

Mouth-Esophagus-Cardiac stomach-pyloric stomach, midgut, intestine, anus

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Circulatory

• Similar to worm, but is open so NO VEINS– System Includes

– Heart

– Seven arteries carry blood to body

– Sinuses to return blood

– Large pericardial sinus surrounding heart

– Blood nearly colorless contains hemocyanin, a copper containing respiratory pigment

– Can clot

100

Respiratory System

• Gills are very prominent during dissection

101

102

Respiration – gills (usually)

Excretory system

• Excretory organs area pair of green glands (similar to our kidneys)

• Green gland consists of a glandular portion, a thin walled bladder, and a duct leading to the renal pore that opens to outside and is just behind the eye

103

104

• Same Order, but different families

• Lobsters are bigger

• Lobsters are marine; crayfish live in freshwater creeks, ditches, or lakes

What’s the difference between

a crayfish and a lobster?

crayfish lobster

Next Class

• Read in Chapter 20 the section over Echinoderms before Thursday class

• Quiz over Grasshopper Anatomy both internal and external

• Echinodermata notes

105

Target Objectives for

Arthropods

• Describe the characteristics of arthropods.

• Explain the main adaptations contributing to arthropod success.

• List the four main groups of arthropods and describe the features of each.

106